ENThe article deals with the question of the origin of the Princes Czartoryski. This problem has long been discussed in historiography, yet it still cannot be regarded as resolved. In response to the recent studies denying the Algirdas (Olgierd) roots of the Czartoryskis, the author proposes a new look at the family lineage, attempting to illuminate the problem of the Czartoryskis’ origin based on a critical examination of beliefs functioning in the memory and tradition of the family in the Old-Polish period. The analysis, scrutinising in retrogressive order the Czartoryski family tradition of the seventeenth and eighteenth centuries, the collective memory of the family in the sixteenth century, and finally, the message of a 1442 document by King Władysław III Jagiellon, which is critical to the issue under examination, provides arguments supporting the Algirdas lineage of the princes. Keywords: genealogy, memory, genealogical consciousness, Lithuanian-Ruthenian knyazi, power elites, Polish-Lithuanian Commonwealth. [From the publication]